Background
Methods
Inclusion criteria
Types of participants
Types of interventions and comparisons
Outcome measures
Study types
Search methods used to identify the studies
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unconscious, Glasgow Coma Scale, coma, craniocerebral trauma, brain injury, sleep apnea
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patient positioning, supine position, spine-/backboard, vacuum mattress
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airway obstruction, anoxia, hypoxia, hypoventilation, hypercapnia, mortality, morbidity, Glasgow Outcome Scale
Data collection and analysis
Data extraction and management
Assessing the risk of bias in the included studies
Measuring the treatment effect
Dichotomous data
Continuous data
Analysis
Missing data
Assessment of the heterogeneity
Assessing the studies that were not applicable to the meta-analysis
Grading the quality of evidence
Results
Studies investigating only the supine position
Study (Year) country
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Patients
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Study outline
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Results
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Notes
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80 adult volunteers, no lung- or airway disease | Interventional study of airway patency under general anesthesia, placing the volunteers in various supine and prone positions. For the purpose of our study: Supine, awake vs. supine, anesthetized. Outcome: open, partially obstructed and obstructed airway. | Incidence of obstruction: | No p-value given. | |
• Supine, awake: 0%; anesthetized: 54% partially obstructed, 36% obstructed, 10% open airway | Loss of airway patency when going from awake to general anesthesia in the supine position. | |||
40 adult male volunteers, 20 obese, 20 normal weight | Observational study of oxygen saturation while awake and during sleep, both in supine position. | Minimum SaO2, mean (%): | p < 0.01 for both comparisons. | |
• Obese group: Supine, awake: 96, asleep: 80 | Shows lower oxygen saturation asleep in the supine position vs. awake, most profound in the obese group. | |||
• Normal weight group: Supine, awake: 97, asleep: 94 | ||||
14 healthy adult male volunteers | Observational study on airway collapsibility under midazolam sedation in supine position vs. 30 degrees elevated upper body. Outcome is critical closing pressure of upper airway (Pcrit) | Pcrit, mean, cmH2O (SE): | p < 0.05. | |
• Elevated upper body: −13.2 (1.3) | Critical closing pressure of upper airway may be regarded as a measure of patency of the airway; the lower supine value means increased collapsibility. | |||
• Supine: −8.2 (1.4) | ||||
48 adult patients, 28 with obstructive sleep apnea (OSA). | Observational study on work of breathing (WOB) in supine position, asleep and awake. Reports data in three OSA groups and control group. | WOB, mean, J/l: | p < 0.05 for all comparisons. | |
• Control group: Supine, awake: 0.70, asleep: 1.16 | An increased WOB may be an indicator of airway obstruction, but no firm conclusion should be drawn from this study. | |||
• Eucapnic, non-obese group: Supine, awake: 1.20, asleep: 2.07 | ||||
• Eucapnic, obese group: Supine, awake: 1.41, asleep: 2.25 | ||||
• Hypercapnic group: Supine, awake: 2.27, asleep: 3.13 | ||||
9 male patients with OSA | Interventional study of upper airway closing pressure during general anesthesia and sitting vs. supine position. Pclose is estimated on to levels of the upper airway. | Airway closing pressure, Pclose, median, cmH2O: | p < 0.01 for both comparisons. | |
• Retropalatal airway: Sitting: −3.47, supine: 2.20 | Airway closing pressure may be regarded as a measure of patency of airway; the lower values in the supine group mean increased collapsibility. | |||
• Retroglossal airway: Sitting: −5.31, supine: 2.67 |
Studies of the lateral vs. supine positions
Study (Year), country
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Patients
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Study outline
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Results
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Favors lateral
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Notes
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Preoperative adult patients
| |||||
13 patients scheduled for gastro-intestinal surgery | Descriptive sleep study of | • Mean average SpO2 (%): Supine: 95, lateral: 95 |
?
| We have used preoperative values only (postoperative values may be confounded). | |
• Mean average SpO2 supine vs. lateral sleeping during preoperative night. | • Mean number of desaturation episodes/h: Supine: 13, lateral: 3 |
+
| Reports p = 0.04. | ||
• Mean number of desaturations pr. hour, defined as sudden desaturation of more than 5% below the patient’s baseline value. | No difference in mean SpO2, but in number of desaturation episodes. | ||||
Adults with obstructive sleep apnea
| |||||
225 adults with known obstructive sleep apnea (OSA) | Descriptive sleep study of nadir (lowest) SpO2 in lateral vs. supine sleeping position. Reports separately on positional patients (with a known position dependent OSA) and non-positional patients. | Nadir SpO2 (mean; %), |
?
| p-values not given. | |
• Positional patients: Supine: 78.9, lateral: 79.5 | Very low values for both groups in both positions. | ||||
• Non-positional patients: Supine: 71.5, lateral: 75.1 |
+
| ||||
110 elderly patients with OSA | Descriptive sleep study of oxygen saturation in supine left and right sleeping positions, reporting time intervals between desaturation episodes (the latter not defined). | Time between desaturation episodes (median; min): Supine: 2.36, left side: 11.54, right side: 12.45 |
+
| Conference abstract only. | |
p < 0.01 for both left and right vs. supine. | |||||
30 adults with OSA | Descriptive sleep study, reporting | • Mean apnea duration + (sec): Supine: 26.6, lateral: 22.8 |
+
| p < 0.0001 | |
• apnea duration | • Mean minimum SpO2 (%): Supine: 82.0, lateral: 86.2 |
+
| Clinically relatively small differences. | ||
• minimum oxygen desaturation | • Mean ∆ SpO2 (%): Supine: 12.6, lateral: 8.3 |
+
| |||
• difference between max. and min. oxygen desaturation | |||||
30 adults with OSA | Descriptive study of average SaO2 in supine vs. all sleeping positions. Reports data sorted by severity of OSA (moderate and severe). | Mean average SaO2 (%), supine vs. all: |
?
| p < 0.01 and < 0.05, respectively, but at least in the severe OSA group the differences are not clinically important. | |
• Moderate OSA: Supine: 93.9, all positions: 95.1 | |||||
• Severe OSA: Supine: 88.0, all positions: 88.4 |
?
| ||||
64 OSA patients | Two groups, one treated surgically for OSA (1), the other just observed (2). Reports data on oxygen desaturation index (ODI; events/h) before treatment. | ODI (events/h): |
+
| p-values not given. Clinically important difference, may have been even larger if supine was not included in all positions. | |
• 1: Supine: 62.7, all positions: 44.6 | |||||
• 2: Supine: 54.5, all positions: 41.1 |
+
|
Study (Year) country
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Patients
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Study outline
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Results
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Favors lateral
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Notes
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---|---|---|---|---|---|
16 male adult patients with suspected obstructive sleep apnea (OSA) | Observational sleep study reporting upper airway closing pressure in lateral and supine position during three sleep stages. | Airway closing pressure (Pcrit, cmH2O) |
+
| P for all < 0.05. | |
• Light sleep: | Airway closing pressure is a measure of collapsibility, lower/negative pressure means less collapsibility. | ||||
Lateral: −2.2, supine: 0.6 | |||||
• Slow-wave sleep: | |||||
Lateral: −1.7, supine: 0.3 | |||||
• REM-sleep: | |||||
Lateral: −2.2, supine: 1.2 | |||||
8 male patients with OSA under evaluation for surgery | Observational study with patients anesthetized and airway closing pressure measured in lateral and supine positions at two areas (retropalatal and retroglossal airway). Airway pressure (PAW, cmH2O) was measured to cessation of air passage. This PAW equals the airway closing pressure, Pcrit. | Airway closing pressure (Pcrit, cmH2O) |
+
| For both areas: p < 0.05. | |
• Retropalatal airway: | Airway closing pressure is a measure of collapsibility, lower/negative pressure means less collapsibility. | ||||
Lateral: −1.86, supine: 2.05 | |||||
• Retroglossal | |||||
• airway: | |||||
Lateral: −3.17, supine: 0.49 | |||||
33 healthy, nonsmoking adult volunteers | Polysomnographic study (PSG) study reporting baseline inspiratory minute ventilation (MV) and upper airway resistance (Rua) in left lateral and supine position. | • MVinsp, mean (l/min): |
?
+
| MV: Small differences, may not be clinically important. | |
Men: Lateral: 7.5, supine: 7.0 | |||||
Women: Lateral: 5.9, supine: 6.0 | |||||
• Rua, mean (cmH2O/l) | Rua: Higher airway resistance in supine position. Reports “significantly difference”, no p-value. | ||||
Men: Lateral: 4.1, supine: 5.8 | |||||
Women: Lateral: 3.4, supine: 6.6 | |||||
30 children (1–10 years) with OSA, scheduled for ear-nose-throat (ENT) surgery. | Observational study of airway obstruction in general anesthesia, in lateral and supine position, using stridor score (1: normal, 4: no airway sound detected) | Stridor score, median: |
+
| p < 0.05 | |
Lateral: 3, supine: 4 | Crude but clinically important outcome. | ||||
17 children (2–11 years), scheduled for MRI. | Observational study of total upper airway volume in left lateral and supine position, using MRI. | Vupper airway, mean (ml): |
+
| p < 0.001 | |
Left lateral: 8.7, supine: 6.0 | Considerable reduction of the upper airway volume in the supine position compared to the lateral. | ||||
Arai et al. [37] (2005) Japan | 18 children (1–11 years) with OSA, scheduled for ENT surgery. | Observational study of airway obstruction in general anesthesia, in lateral and supine position, using stridor score. | Stridor score, median: |
+
| p < 0.05 |
Lateral: 3, supine: 4 | Supine position reduced the airway obstruction. (Addition of jaw thrust and/or chin lift reduced the obstruction further.) |
Study
(Year)
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Patients
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Study details
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Results
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Favors lateral
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Notes
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Country
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Adults with cervical spine cord injury (CSCI)
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42 adults with existing CSCI (46% of the identified candidates in a region) | Observational sleep study of RDI in supine vs. other sleeping positions. | RDI (events/h), mean: |
+
| p < 0.0005 | |
Non-supine sleeping positions: 15.3 | No data for lateral position per se. | ||||
Supine position: 23.6 | |||||
Children with possible obstructive sleep apnea (OSA)
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60 children (under 3 years), referred because of possible OSA | Observational data from previous sleep study. | RDI (events/h), mean: |
+
| p = 0.02 | |
Non-supine sleeping positions: 7.2 | No data for lateral position per se. | ||||
Supine position: 18.5 | |||||
Adults with stroke
| |||||
120 stroke patients investigated more than 72 h after onset | Observational study of RDI in different sleeping positions. | RDI (events/h), mean: |
+
| p < 0.0001 | |
Left lateral position: 14; Right lateral: 12 | Numbers for left and right lateral are not reported in text or table, but estimated from figure. | ||||
Supine: 29 |
Study
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Patients
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Study details
|
Results
|
Favors lateral
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Notes
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(Year, country)
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Children with obstructive sleep apnea (OSA)
| |||||
Zhang [47] (2007) China | 45 children (3–13 years) with OSA | Observational study of AHI in lateral vs. supine sleeping positions, measured by PSG. | AHI (events/h), median: |
+
| Reports IQR, not SD. |
0 in left and right lateral position, 11.9 in supine- | P < 0.001 and p = 0.003, respectively. | ||||
do Prado [45] (2002) USA | 80 children (1–10 years) with suspected OSA | Observational study of obstructive AHI in lateral vs. supine sleeping positions, measured by PSG. | Obstructive AHI (events/h), mean: |
?
| Does not report SD. |
7 in lateral positions, 8 in supine- | No significant difference. | ||||
Nisbet [50] (2014) Australia | 76 children with Down syndrome (DS), 76 without DS | Observational study of AHI in DS, with matched controls. | AHI (events/h), median: | We report data from control group, as DS may be too indirect. | |
REM sleep: 8.3 in non-supine positions, 17.8 in supine position |
+
| ||||
Reports IQR, not SD. | |||||
Non-REM: 4.6 in non-supine positions, 5 in supine position. |
?
| ||||
In Non-REM sleep the difference is not clinically important. | |||||
Adults with OSA
| |||||
Kim [48] (2011) Korea | 75 adults with OSA | Conference abstract of observational study of AHI in supine sleeping position vs. all other positions. | “This study confirms … that OSAS is position dependent in more than 50% of patients and non-supine position would lower the AHI…” |
+
| No data given, should be interpreted with caution. |
Sasai [34] (2011) Japan | 30 adults with moderate and severe OSA | Observational study of obstructive AHI in supine vs. all sleeping positions, measured by PSG. | AHI (events/h), mean: |
?
| Does not report AHI in lateral position per se. |
Moderate OSA: 27.0 in all positions, 27.5 in supine position. | |||||
In the severe group: p < 0.05, but not regarded as clinically significant difference. | |||||
Severe OSA: 77.1 in all positions, 79.9 in supine position. | |||||
Li [46] (2006) China | 54 adults with OSA | Observational study of AHI in in lateral vs. supine sleeping positions, measured by PSG. | “…the overall AHI in supine position was higher than in lateral…” |
+
| Article in Chinese, only abstract in English, no data. |
p = 0.000 | |||||
Adults with stroke
| |||||
Svatikova [49] (2011) USA | 18 adults with stroke | Randomized crossover study of positional therapy for sleep apnea in stroke. | AHI (events/h), mean (no intervention): |
+
| Reports IQR, not SD. |
No p-value given. | |||||
27 in non-supine positions, 49 in supine position. |
Grading the evidence
Discussion
Outcomes
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Illustrative comparative risks (95% CI)
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№ of participants
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Quality of the evidence
| |
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Assumed risk
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Corresponding risk
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(Studies)
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(GRADE)
| |
Supine position
|
Lateral position
| |||
AHI - Adults with sleep apnea
| The median AHI (episodes/h) in the control group was 52.4
| The mean AHI (episodes/h) in the intervention group was 22.8 fewer (29.1 fewer to16.6 fewer) | 2780 (20 observational comparisons) 1
| |
AHI - Adults before and after surgery
| The median AHI (episodes/h) in the control group was 26.0
| The mean AHI (episodes/h) in the intervention group was 10.4 fewer (15.2 fewer to 5.6 fewer) | 1448 (3 observational comparisons) | |
AHI - Patients with stroke/TIA
| The median AHI (episodes/h) in the control group was 23
| The mean AHI (episodes/h) in the intervention group was 13.9 fewer (20.9 fewer to 6.8 fewer) | 196 (2 observational studies) | |
AHI - Infants and small children
| The median AHI (episodes/h) in the control group was 2.5
| The mean AHI (episodes/h) in the intervention group was 0.74 more (0.6 fewer to 2.08 more) | 190 (9 observational comparisons) |